The present invention relates generally to eye testing apparatus and more particularly to devices for accurately determining the proper height for bifocal segment lines.
When corrective lenses are to be provided with bifocal segments, it is extremely critical to the satisfactory performance of such eyeglasses that the segment height be properly positioned with respect to the corrective lenses such that both the bifocal segment and other portion of the corrective lenses will be located in proper relationship to the user's line of vision. As may be presumed, it is very important that this measurement be accomplished while the user is wearing the eyeglasses as the relative positioning of this segment line with respect to the user's eyes is of critical importance. This measurement problem is further compounded by the fact that present day eyeglass frames take a wide variety of shapes and sizes ranging from generally circular in shape to various oval configurations. Additionally, any such measuring apparatus should also be capable of accommodating the so-called frameless eyeglasses as well as wire rim frames, etc.
While various devices have been developed over the years for use in determining this measurement, none of these devices have proved to be totally acceptable. Many of these devices are difficult and/or complicated to use thus requiring substantial amounts of time be expended in obtaining the desired measurement. Others of these devices do not tend to be sufficiently accurate or may result in movement of the eyeglass frames during a critical portion of the measuring process. Still other devices may be extremey well suited for use with a particularly shaped frame member but may be virtually unusable with respect to other different shaped frame members.
Accordingly, the present invention provides a segment height measuring device which overcomes the problems heretofore encountered with such devices. The segment height measuring device of the present invention is designed to be fabricated from lightweight transparent plastic and is provided with clamp means which may be adjustably fitted to virtually any shape frame member. The apparatus includes a sliding member which is preferably fabricated from a transparent colored plastic so as to distinguish its location from the otherwise clear measuring device upon which is imprinted appropriate indicia. Thus, by merely moving the slide member into the appropriate position, the coloring thereon will provide a clear indication of its location to the wearer of the eyeglasses thus assisting in obtaining the proper measurement for the segment height line. The ophthalmologist or optometrist need thereafter merely read the correct positioning from the indicia scale provided on the member and will then be assured that the lens manufacturer will be able to accurately position the segment height line.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.